Notes from soggy bottom

Thursday, March 29, 2007

Walking through the Luneau mire

Come with me and take a frame-by-frame walk through the Luneau video. Maybe this way I can show exactly how incorrect are the claims by Sibley, Bevier, Collinson, etc. that the video shows diagnostic features of a Pileated, and no features that are inconsistent with a Pileated.

By the way, I think the convention of numbering these frames to 0.1 ms (33.3, 366.7, etc.) is silly. The extra decimal place is unnecessary, and I'll call these frames 33 and 367. The video from which these frames are extracted is copyright David Luneau.

We start here at frame 167, where the bird is first emerging from behind the tree trunk. I'm going to focus primarily on the bird's right wing, as that is generally the one presented best to the camera. Here we see this wing in mid downstroke, showing its underside. Two things to note here: First, the white of the underwing in the image is bordered on all sides by a darker fringe; secondly, the wing is strongly flexed at the wrist, giving a distinctive bowed shape.

Next is frame 183. Here the flexed shape of the wing is especially evident. There are also four distinct dark blobs around the edges of the wing: two on the upper (trailing) edge, one on the lower (leading edge), and one at the tip. And here we first see the pattern that holds true for the rest of the video. Note that each of these blotches aligns with a darker shadow in the background. Even the distinct dark wingtip is in fact aligned exactly with the lower end of a shadow visible in f167.

The next few frames are a blurry indistinct mess as the wing reaches the end of the downstroke and then undergoes the rapid folded upstroke. So we'll jump ahead.

Here at frame 233 the wing once again begins to show something other than gray smears. We see the large white underwing area bordered on the left and the upper right by darker areas. Again, these dark areas align with shadows behind the bird.

Moving on to frame 250, the beginning of the downstroke, one of the most dramatic changes is the great increase in the apparent size of the white underwing from f233. It seems the wing, though appearing fully raised in f233, was still partially folded. Also note that the wing is already flexed strongly at the wrist. This is one of the frames that has been said to show a dark trailing edge. I see four dark areas bordering the wing: one on the left edge adjoining the edge of the tree trunk, a distinct one at the upper left , a smaller one at the top, and a general diffuse dark area to the right of the wing (close to the wing's leading edge). Once again, all align with background shadows. Let's look at the next frame and see where they go.

Here in frame 267, at first glance it appears that the four black areas from f250 have traveled with the wing. First glances are deceiving. Look again, and you will see that the first black spot (the one on the left) is still where it was... attached to the tree trunk and separated from the wing. The second spot has traveled down the trailing edge of the wing, remaining aligned with the same shadow. The now much larger black area at the trailing edge of the outer wing is aligned with a much larger background shadow that the wing is now passing in front of. And the black spot to the right of the bird now appears to be a black leading edge to the wing. Yet again, all black fringes are aligned with and attributable to dark background areas. The strong downward bend of the wing at the wrist remains very clear.

In the next frame (283) the wing is surrounded by black beads. The large black fringe that was on the outer trailing edge of the wing in f267 has now shifted proximally (remaining aligned with the shadow) and broken in two. A new black spot has appeared on the outer trailing edge where (lo and behold) the wing has passed in front of another background shadow. And at the wingtip, a darkish wingtip is forming where (guess what?) the wingtip image has begun to interact with yet another background shadow. Meanwhile on the leading edge, the black spot has condensed, remaining aligned with the background shadow. All through the video we see this: Black fringing blobs that remain aligned with the background features as the wing moves in front of them. There is no reason to treat any of these black blobs as real. And of course, the wing remains strongly bowed.

Here in the next frame (300) on the right wing we see a prominent black wingtip. Look back at f283 and especially f267, though, and notice how the shape of that black wingtip closely matches the shape of the background shadow in front of which the wingtip is now passing. The other black blobs along the wing fringe have largely faded. Now, for a change, look at the left wing which here is probably presented as well to the camera as it ever is. It seems to show a gray fringe around both trailing and leading wing edges. More prominent thougs is the black wintip. This one looks real, as it is independent of the background. It is of course smeared into a smooth arc and its actual shape is not discernable. Another very interesting feature on this wing is the apparent zonation in the white: bright on the outer wing, dingier on the inner wing, possible a darker indistinct border at mid-wing. This has been described as showing a Pileated's "bright white primary bases," presumably contrasting with the duller white underwing coverts. However, this fails to take into account the bend of the wing at the wrist and the forward rotation of the wing in direct flight. The outerwing is held more vertically and rotated more towards the camera than the inner wing; this is likely adequate to account for the underside of the outer wing appearing brighter in this image. And in some other images the pattern is reversed.

Skipping through the blurry upstroke again to frame 350. Just as in f233, we see what looks like a fully raised wing, except that it appears short relative to the next frame so it seems to not be fully extended even if it is fully raised. And we also see a distinct black border to the left (presumably) trailing edge of the right wing, at least on its proximal portions. This is another frame that has been said to clearly show the Pileated's black trailing edge. And in this case there is not a background shadow to blame it on. The quite reasonable suggestion as to why it is most prominent proximally is that motion blur is least there. So in the next frame, we should expect to see it contract somewhat but persist on the proximal edge. And in the next frame, what we do see is...

(frame 367) Hmmm... in fact it has disappeared proximally and been replaced distally by a big fat black fringe on the outer wing and wing tip. And, as usual, this big fat fringe aligns with a big fat background shadow. There's no hint at all of the black trailing edge on the slowest-moving proximal portion of the wing. So what was going on in f350? Well, there are two things to consider. First, in f350 the wing was evidently not yet fully extended, and there is also the issue of the left wing which should be in the image somewhere. I can't account for exactly where that black fringe came from, but there's not much clear indication that it came from a real black edge on the wing when you look at this subsequent frame. There's no suggestion of it on frames 467 and 583 when the wing is once again in similar orientation. Another thing to note here relevant to the "bright primary bases." Here, it is clearly the inner wing that looks brightest. Once again, the vertical portion of the wing looks brighter than the more downward-facing (due to the bend at the wrist) portion of the wing, as would be expected.

In the next frame (383) the rapidly-moving wing is dissolving into a hook-shaped blur (hook-shaped from the continuing strong bend at the wrist). The big black border from f367 is reduced to faint hint, still aligned with shadows.

In the next two frames the right wing passes in front of relatively plain background. Both here (frame 400) and below in frame 417 it is worth noting that the right wing white underwing shows a gray fringe around all edges. What should we make of this?

Here in f417 the left wing also show a quite uniform gray fringe around all its edges. Note that though the wing itself is strongly motion blurred, the the fringe is more consistently narrow around all sides, because it is an imaging artifact not a part of the wing.

I could repeat this for every frame but it would get tedious. The pattern is established: black fringe artifacts that occur in association with background shadows along all edges of the white underwing; wings held bowed with a strong bend at the wrist throughout the downstoke, no consistent appearance of real black on the underwings anywhere but at the outermost wing tips. I do want to sample a few frames from farther on to clarify a few points.

here in frame 467 is the next time the wing is held upward, comparable to frame 350. Again, in comparison to the next frame, the wing is clearly not fully extended. Here we see a nice dark edge to the underwing: a leading edge. Of course, it aligns with the background shadow. No reappearance of f350's apparent broad black trailing edge.

A very interesting thing happens here in frame 483. As the wing extends and begins the downstroke, it aquires a quite prominent black leading edge that does not align with a background shadow. The large black spot near the wingtip does align with a shadow, of course. So this balances f350 in a sense: one each of black leading and trailing edges that are not readily accounted for by interactions with background shadows. It would be folly to base an ID of this bird on either.

And finally, I like this frame for its comic value. This is frame 700, the end of the upstroke two wingbeats later. I count at least three black wingtips among the two wings, and black on both the leading and trailing edges of the right wing.

To summarize and reitterate: The black edge features imaged around the wings of the bird in this video do not represent real features of the bird. There is no evidence at all that this bird has a black trailing edge to its wings. The conclusions of Sibley, Bevier, Collinson, etc. about this matter have been based entirely on misinterpreted and selectively interpreted image artifacts, and should be disregarded. Sibley was quoted as saying that Collinson had demonstrated just how Ivorybill-like a bad video of a Pileated can appear; in fact what they have both demonstrated is just how bad experienced birders can be at interpretation of bad video.

Of course, no evidence for a black trailing edge does not prove the presence of a white trailing edge in such a poor quality video. Both species have black markings on their underwings (other than the wingtips) and the video does not resolve any of these. I have generally promoted the conservative approach that nothing can be inferred about the locaion of any hypothetical black on this bird's underwings from this flight sequence. Others have argued, however, that the Pileated black trailing edge is generally much wider than the Ivorybill medial bar, and it should have been clearly resolved in multiple frames if it were present. Cornell's experiments with shooting videos of painted models using the same video camera under the same circumstances suggested this. Still, it remains that the distinguishing characteristics of the underwing pattern are not resolved in the video for the case of either species, at least in the flight sequence I just discussed. But...

There are a few frames of the bird's underwing before it disappars behind the tree. These are the controversial frame 33 and adjacent images. As I have said in previous writings, I tend to agree that what is seen here is the underside of an extended wing, not the topside of a folded wing. Let's look at these frames again in light of what we've learned from the rest of the video:

Infamous frame 33. Best interpreted (to my thinking) as the trailing edge of the underside of the bird's right wing, extended as the bird begins to launch from the tree. I see just white. The faint gray fringe is barely present, no stronger than the gray artifacts present around all the white wing edges in other frames examined above. Still, there might be an unresolved black trailing edge.

Move on to the next frame (50). The wing is travelling to our right and being eclipsed behind the tree. We are only seeng the rearmost few centimeters of the underwing. Predominant color? WHITE. Faint gray fringe is just like the artifacts seen everywhere else. If this were a pileated underwing there should be no white left at this point. In Sibley's interpretive sketches of these frames he has drawn a razor-thin black trailing edge to explain this. The trailing edge is so thin, we are told, because of defocus, white bleed, and motion blur. This is well and good, except than none of these will make white bleed around the corner from behind a tree, which is exactly what Sibley has drawn the white doing.

In the next frame the wing has vanished entirely from view; all we have left is the end of the tail. Before you get excited about those two black pixels on the edge of the tree trunk above the tail, look back at the previous frames and you will see they are a fixed portion of the tree. They are not part of the bird.

Indeed, the bird appears to have a white trailing edge to the underside of its right wing. The black trailing edge had every chance to reveal itself in these two frames, and was still a no-show.

I'm not going to repeat my whole arguments about flight mechanics again here; I've covered them extensively in earlier posts. That bowed wing shape is characteristic of this bird in every visible wingbeat and is very unlike the wing dynamics shown in every Pileated video I have seen. We can't say that it is Ivorybill like, but we can say it is not Pileated-like. I wish someone would produce some comparable take-off footage of other Campephilus species.

At the end of our walk we find that, in contrast to the widely promoted view of Sibley et al, the Luneau video does not at any point show any distinctive characters of the Pileated's underwing pattern; indeed there is a strong indication that the bird has a white trailing edge to its underwing. It also shows flight mechanics that are clearly and dramatically atypical for a Pileated Woodpecker. In the exact opposite of the views promoted by Sibley and others, we find nothing in this bird that is inconsistent with its being an Ivory-billed Woodpecker, and some features that are clearly inconsistent with its being a Pileated Woodpecker.

ADDENDUM: I've had a couple of anonymous requests to give my assessment of the second flight sequence in Mike Collin's 2006 Pearl River video. I just looked at it again (his enlarged, lightened version with the frames numbered). I have a difficult time making out any detail of the wing postures other than a general sense of when each downstroke begins and ends. I can't really resolve more than that. For the first 9 frames as the bird launches and rolls I can't even resolve that much very well. From frames 10 onward I make out a flap every 4 frames, or 7.5 beats/s, but no more detail. I don't feel that I can make any assessment of that bird's wing postures in flight in order to make any comparison to either the Luneau or known Pileated videos.

Comments: Sign them with your real name and stay focused on issues raised directly in this posting, please. There are many other venues for generalized, wide-ranging, and anonymous woodpecker discussions. Thank you.

Tuesday, March 27, 2007

Gingerbread

I finished the paint job on the upper part of the front of our porch, so I was finally able to take the scaffolding down and let it be seen for real. All that woodwork is original (except for minor repairs), dating back to the 1880s. It has never been "tarted up" like this before, though. By San Francisco or Eureka Springs standards this color scheme is actually fairly mild for a Victorian, and in Colorado it would be middle of the road. But in these parts it is rather far left-of-center. Hey, we have the only surviving original 19th Century Carpenter Gothic porch in the entire county, and now no one who passes by is likely to miss it! Cars have already begun slowing noticeably.

Under the eaves are a series five of inscriptions. They are for the most part blessings and greetings. Each is a quotation in a different ancient or classical language, and each is written in an alphabet appropriate to the language. I did use some license on one script, though. In one case I used an alphabet that was designed to be highly flexible and adaptable, and I came up with my own modifications to make it into a more decorative script.

And how are everyone's ancient languages? Y'all can all read these, right?

Sunday, March 18, 2007

Tracking Chimney Swifts

From Austin TX:

**************The first Chimney Swifts of 2007 have been spotted on the Gulf Coast. Once again this year we will be plotting the swifts' movements northward over the next few months. Please let us know when you see the first ones in your area. The results will be posted on our web site at:

Thursday, March 15, 2007

Martin Collinson's Ivorybill article

-- He interprets artifacts as plumage. As I have pointed out several times here, the Luneau bird shows black fringes on the leading edge of the underwing as often as it shows black fringes on the trailing edge of the underwing. Ergo, apparent black fringes must not be taken to indicate anything about the bird's actual coloration. There is nothing resolved in the underwing pattern but a lot of white with a black area at the tip, which both species share.

ADDENDUM: I have just frame-by-framed through the Luneau video one more time. In almost every single case, every black fringe seen on the birds wings can be seen to align with a darker area in the background. When this happens the black fringes often occur on both edges of the wings, and in subsequent frames if they reappear they do so fixed relative to the background, not relative to the moving wings. The only exceptions to this are the small black wingtip area, which appears most consistently at full downward extension. The supposed broad curving black area in frame 366.7 that is said to represent the outer portion of the black trailing edge of a PIWO is exactly aligned with the background shadow, and it disappears on the next frame when the wing has moved past this shadow. The black arcs a the ends of the wing in frame 300 are (on the right wing) aligned with a background shadow and (on the left wing) clearly a streak left by a rapidly moving wingtip. There is no consistent occurence of a black trailing edge or curved black wingtip; these things appear for one frame at a time and then disappear in the next frame because they are not real. Collinson has stated on his blog that "Sibley et al. have shown why the Luneau bird wasn't an Ivory-bill." This is only true if you accept video artifacts as reality.

-- He totally misses the boat on flight mechanics (as has virtually everyone else) by focusing on wingbeat rate. There is a much bigger story, in that the shape of the Luneau bird's wing strokes are markedly different from that shown by the Nolin video or any other video of a Pileated I have seen. The Luneau bird does not fully extend its wings at the top of the upstroke, and holds them in a strong downwardly-bowed arc on every downstroke. ALL pileated videos I have seen show wings that are fully extended on completion of the upstroke and held essentially straight out downstroke on every wingbeat other than the first one or two after launch (while the bird is still rolling to attain proper flight attitude). This is very evident in Collinson's side-by-side frame comparisons, and Sibley's sketches showed these dynamics as well. Yet neither of these authors have made any mention of it nor offered any explanation. Is this flight Ivorybill-ish? No one can say, we have no comparison material. But it is definitely not at all Pileated-like. The wingbeat rate issue is minor in comparison.

Wednesday, March 14, 2007

A bit more about the Avian Phantoms

One final thing I want to do here on this topic of overlooked and unseen birds...

Though it isn't possible to rule out the persistence of the phantoms, I think it is possible to make some more ballpark estimates, this time of the maximum plausible population size that could be consistent with the data we have. Swallowing the big frog first, I'll start with the Ivory-billed Woodpecker. Please accept that I am going to use the most generous and optimistic interpretations of the existing data that I think are plausible, and don't fill up my comments box with all the (well-known) alternative interpretations that yield much lower (i.e. zero) population estimates. We can take that as a given.

Some very generous, hopeful, and optimistic things have been said about potential population sizes for this species, such as "a population near carrying capacity in the White River NWR" and "as many as 10 pairs on the Choctawhatchee." Most of these were said early on, and I think it is safe to say that they have proven untrue. For the Big Woods, given something on the order of 20,000 hrs of field time in recent years (I'm guessing at that number, it's 10 parties in the field 10 hrs a day 5 days a week for 40 weeks), that gives 2000 square km covered (obviously a lot of duplicate coverage there) and no nesting pair found or even hinted at. I think the most generous plausible interpretation of their 10 or so "robust" sightings, ARU results, and one lousy video is the presence of only 1 or 2 non-breeding birds that might not even be in the area all year. I also think it is clearly implausible to expect there to be 10 pairs in the Choctawhatchee area. With a team of full-time observers, brief sightings are happening every few weeks; the more robust sightings with more detail have come only a couple of times a year. One thing I am not buying in to is the notion that the Ivorybill is preternaturally wary and elusive. To me, this low encounter rate indicates a very low abundance, no more than one bird per roughly 10 square km, not magical evasive powers. That doesn't leave anywhere near enough room for 20 adults plus young of the year in that river basin. There is another point also. If there were that many Ivorybills in the Choctawhatchie, one might expect similar colonies to show up in other rivers in the Florida panhandle. Dispersal between basins should not be a big problem. But if we had 10 pairs in the Escambia, Perdido, Coldwater, Blackwater, Appalachicola, etc. then we'd be talking about 100s of Ivorybills in an area with many highway crossings and swamp-front houses. Such a density in this area would not be overlooked for a year, much less 50 years. Birders traversing I-10 would see Ivorybills cross the highway in front of them on a regular basis. In fact, this is only reported to happen every few decades (and then in Louisiana, not Florida). I think the most generous interpretation that can be put on the Choctawhatchee at this point is a few individuals, maybe a pair plus a couple of non-breeding offspring, and a bunch of Blue Jays that have gotten very good at imitating Ivorybill calls to confuse the field workers and the ARUs. And I think we also must conclude thay this density is not "typical" for the panhandle rivers; that is, there is not a pair or two in every swamp down there, just a very fortunate few.

What about the Pearl, Atchafalaya, Congaree, all the other places? Well, for the Pearl, the same arguments apply as above. If there were more than an isolated pair (maybe two?) in the area, photos and multiple sightings by multiple observers would have almost surely happened by now. Mike Collins has not been the only camera-equipped birder there in recent years. The Atchafalaya is certainly big, difficult of access, and mostly private. But even our resident Ivorybill-searching duck hunter down there (the enigmatic "Choupique") only claims a couple of personal sightings in his lifetime. Again, this suggests to me no more than one bird per every 100 square km in the basin. This is only a handful of pairs at best. As for all the other areas, we have isolated sightings, and those only very occasionally. I personally have probably spent over 1000 hrs in "potential Ivorybill habitat" in Georgia and several other states, without a glimpse, kent, or rap, not even a suggestion of such a thing. Once again, this implies less than a bird per 100 square km.

My "optimistic" conclusion from all this is not in fact very optimistic. If we have an average density of <0.01 bird per square km in our approximately 10,000 square km of this habitat, then we have a global population of less than 100 birds. Personally I feel that is too generous, and a number of no more than a few dozen is all that is likely supported by the evidence. This might not sound too dreadful at first glance; after all we've had other species drop to those levels and then rebound. The difference though, is that those Cranes, Condors, and Warblers were all in one place, where they could be monitored and managed and where they could find each other. These couple of dozen woodpeckers, if they exist, are heavily dispersed, with no more than single digits in any individual State. And this is an upper estimate; the lower estimate would be in the single digits worldwide. There is no way to describe this other than with words like "bleak," "dire," and "desparate."

Having now gotten the big frog out of the way, the remaining two (Eskimo Curlew and Bachman's Warbler) are relatively easy. During the latter decades of the 20th Century, they were reported at roughly the same frequency as the Ivory-billed Woodpecker: a few reports a decade, and "good" reports less than once a decade. So, skipping all the intermediate steps, I come to the same conclusions, and the same bleak estimate for an upper limit for the population that is consistent with "phantom" status: a few dozen at best. Zero at worst. But the difference between zero and slightly more than zero is the difference between night and day.

Monday, March 12, 2007

Missing Birds 2: The Phantoms

Continuing my thoughts from an earlier post, I am naturally lead to the matter of North America's avian phantoms. There are, of course, three of these: Eskimo Curlew, Ivory-billed Woodpecker, and Bachman's Warbler. For some reason, one of these birds has ignited high passions and fierce debates for many, many decades; the other two have generally been approached in a more cool-headed, though still controversial, fashion. I'm going to pretend for the moment that all three of these species can just be dealt with as birds, not religious icons.

The prime question about all of these phantoms is always this:

Is it possible that they could have escaped detection for decades at a time yet still exist?

My back-of-the-envelope numbers suggest that in fact it is possible. Indeed, if they have managed to survive with populations numbered in the 10s or less, it might not only be possible, but likely and expected that many, many years would elapse between sightings. But, what is the difference between these birds and species like the Snail Kite, Whooping Crane (population formerly numbered in the teens), Kirtland's Warbler, and other birds with very small populations that are seen all the time? Well, it seems to me the difference is quite simple: We don't know where to look. We lost track of them. Without knowing a specific, small area to search in, the difference between very few birds versus no birds at all becomes extremely difficult to determine. Statistically, the amount of effort needed to either rule out or have a good chance of unequivocally detecting the presence of a small relict population lurking somewhere within a large area can be enormous.

But, don't we know where to look? Well, what we know are general patterns of historical occurence, and locations of recent unconfirmed sightings. However, this doesn't narrow our search down to small places and specific times where we'd stand a good chance of finding the birds if they did exist. Just because there have been multiple reports of Eskimo Curlews from Galveston Island doesn't mean that this is an especially favored spot for the species; it just means that this is where most of the birders on the Texas coast are. The nesting and wintering grounds for all three phantoms are in places that have not been especially swarming with birders and ornithologists during the last 50 or 100 years. Even the bottomland habitats of the Bachman's Warbler and Ivory-billed Woodpecker, though located in the heavily-populated eastern US, are probably the most inaccessible habitat in the region. It is not so much a matter of being remote or impenetrable. It is more about roadlessness and "No Trespassing" signs.

There's a fundamental problem with searching for low-density birds of poorly-known distribution by using targeted searches. If you focus intense effort in a small area, you are gambling that you picked the right spot. Suppose (oh no, here he goes again), that you've got ten areas, each of them one square km in size, and there is a single bird somewhere in the whole 10 square kms. This bird is one of those "typical" birds I talked about before, that you will on average find once every 10 hrs if there is one of them per square km. You have 100 hours of effort to put into searching for that bird. If you focus all 100 of those hours on a single square km, you have about a 10% chance of finding the bird. But if you spread that effort out, 10 hrs in each square km, your odds of finding the bird are closer to 70%. In the targeted search, if you guessed right you will almost surely find the bird multiple times, but 9 out of 10 times you will have guessed wrong. In the dispersed search, you stand a better chance of finding the bird at least once, though you are unlikely to find it more than just once or twice.

If you don't like these sorts of hand-waving calculations, just do an experiment that many of us do every year. On some June morning, go out and spend 4.5 hours walking around your favorite park, focusing your effort in a small area. The next morning, go do a Breeding Bird Survey, making 50 very short visits to 50 different, randomly selected spots. Then compare your species tallies for the two mornings. Odds are, you detected quite a few more species with the dispersed effort than the concentrated effort. This same phenomenon is why Breeding Bird Atlas projects have turned up so many surprises. Getting observers spread out and dispersing their effort revealed occurences and patterns that had been missed by many decades of clumpy, clustered effort.

So what is the answer about the phantoms? Even if one or two intensive searches (or a lucky chance encounter with a tourist and a camera) were to prove the continued exsitence of one of these species, we still would hardly know anything about the totality of the situation. Could some form of "Birding Blitz" help sort this out? If it were possible to get large numbers of experienced birders to each contribute a modest amount of (personal, volunteer) effort, spread throughout the areas of possible phantom occurence, would we emerge with more confidence in our assessment of whether or not these species still exist, and if so where and how many? In the past, it has been possible to pursuade large subsets of the hard-core birders to break their usual routines and go places they never would have gone otherwise, in the name of science and discovery. Is the notion of a "Curlew Blitz" in the prairies and western gulf coast in the spring, and paired "Woodpecker and Warbler Blitzes" in the bottomlands in winter and spring even worth thinking about? It might be more demanding on the observers than the Atlas projects were, especially the "Swamp Blitzes." Those might involve boats and private property far more than did the average Atlas block. But just for the sake of argument, if we could get say 200 people to each contribute 10 hours a year for each of five years, we'd have 10,000 hrs of observer effort. Might that be enough? Would we need 1000 people and 20 hrs a year to give 100,000 hrs of effort to be confident that we'd find the phantoms if they are out there? Could such a thing even be carried out? The "Curlew Blitz" would at least turn up a whole bunch of other shorebirds, including some nice rarities. The "Swamp Blitzes" might be harder to tempt people to volunteer for, especially since you'd need to have people with good ID and documentation skills for any of these efforts, similar to what is requres for the Breeding Bird Survey, and those folks are often already over-committed as volunteers.

Saturday, March 10, 2007

The Lunatic Fringe

The current issue of Birding publishes an interesting survey by Hayes and Hayes of opinions and beliefs about the Ivory-billed Woodpecker and the recent reports. At least statistically speaking, the "lunatic fringe" turns out to be the hard-core atheists who are certain of the species' extinction (<4%), not the true believers who are certain of its continued survival (21%). Just in reference to the actual recent evidence that has been made public, both of the "definite" camps are small minorities (<10%) each, with the large majority (>80%) clustered in the "possibly/probably" middle awaiting further developments or lack thereof. The fact that this contrasts so sharply with the impression given by the blogosphere and mass media of extreme polarization should not be a surprise to anyone who has paid much attention to mass culture and cyber culture in recent decades. Hyped (often deliberately manufactured) polarization that overwhelms and supresses the reality of more rational, diverse, and flexible feelings is the way of things now. This is true for culture, politics, religion, popular science, and everything else. Just tune it out.

Over at the Lunatic Fringe Home Page, Tom Nelson has already begun his attempts to discredit one of the article's authors.

Thursday, March 08, 2007

Missing birds

I have long thought that birders tend to drastically overestimate the percentage of the continent's individual birds that we actually manage to see or hear. I know in the course of my daily routine I almost never come across other birders, and I am one. If I hardly ever come across them, it seems that a bird, going about its own, bird-thing-focused routine, would almost never happen to stumble within binocular range of a birder. So, indulge me in another of my little back-of-the-envelope calculations, and see if we can put some fast and loose numbers to this.

I have developed a general rule of thumb that in one hour spent in the field an experienced birder will find roughly the equivalent of all the birds in 0.1 square kilometer of land. This is very approximate, and of course not universal across species. Turkey Vultures are much more obvious than this, and LeConte's Sparrows are much better at staying hidden. But for the run-of-the-mill land bird in your average forest-field-and-park habitats, I find this rule of thumb to be a good rough estimate. For instance, I find it takes a couple of hours of criss-crossing my 16 ha farm to feel like I have seen the bulk of the birds on it (for the SI challenged, ha = hectare = 10,000 square meters; 100ha = 1 square km. Roughly 1 ha = a bit more than 2 acres). Or you can think of it this way: if you cover about 1 km of distance in an hour's birding, you have seen most of the birds within 50m either side of your path, and missed most of the birds farther away than this. Again, this is all very approximate, and there are infinite variations depending on whether you are sitting still, walking, bicycling, driving, in prairies, in deep forest, etc. etc. But we're doing that order-of-magnitude, back-of-the-envelope thing, so I'll take 10ha/hr as the generalized conversion factor for hours afield to area covered.**

So, how much land does an average, active birder cover in a week? I'm going to restrict this to the sort of birder who is experienced enough to identify rare birds consistently and accurately, AND who reports what s/he sees to the birding community as a whole, at least the rarities. In the birding world, if a rare bird sings in the forest, and the person who hears it doesn't tell the RBA, listserv, local field notes compiler, or rare bird committee about it, then that bird really didn't make a sound. Let's say this typical birder has a typical job and other responsibilities, and manages to get out for a few hours most weekends, say something like 3-5hrs. So, we'll estimate that this typical birder, in a typical week, sees something very roughly equivalent to all the birds in 30-50 ha. This may be generous; a lot of these sorts of birders can't swing this much time every week, all year. But we'll go forward with this.

OK, so how many of these birders are there? Let's just look at the contiguous 48 States. A number like 10,000 might be a good ballpark guess. There are about 50,000 Christmas Bird Count (CBC) participants in this area each year; there are something like 70,000 checklists submitted to the Great Backyard Bird Count annually. But both these numbers include double counting; they also include a lot of birders who are more casual and/or less likely to report their findings than the type of birder I described above. A total of 10,000 averages out to roughly 200 per State, or about one per 30,000 population (i.e. in a city of a million people, there would be thirty of these birders). These numbers seem to be of the right magnitude to me. If you look at the State listservs, or the regional reports in North American Birds, this is in line with the number of different names that you see popping up. So NOW.. we multiply our ballpark estimates:

Ten thousand birders covering 30-50ha per week gives us about 3,000 to 5,000 square-kilometers-worth of birds found during an average week, over the entire lower 48. But, the total land area of the Lower 48 is about 8,000,000 square km. So... all these birders, in an average week, find about 1/2000th of the birds here. For every rare bird that someone finds, there are THOUSANDS of others just like it than no birder has seen or ever will!

Now of course there are cases where this just plain isn't true. Big conspicuous birds of open country are probably found much more reliably than this, especially if they are prone to congregating in well-defined, identifiable areas. A much higher fraction of Trumpeter Swans almost certainly gets found, for instance. But Gyrfalcons? Not so sure. And stray passerines that are not of the feeder sitting sort, like MacGillivray's Warblers in the east? Or rare breeders in rural habitats? We find only a TINY fraction of these. There will also of course be a bias in favor of species that frequent more heavily-birded habitats, such as feeders, city parks, rural/suburban matrices close to major metro areas, coastal and interior wetland "hot spots," and the like; and a parallel bias against birds of underbirded habitats, like large continuous forest tracts, western rangelands, and high mountain habitats.

It is tempting to just multiply this by 52 and conclude that in a year, this nation of birders will find about 1/40th of the birds in the continent. And this would be true if either the birds or the birders moved about randomly across the landscape. Of course, neither of us do. Birders tend to go back to the same places from week to week, and many birds tend to stay within small home ranges for weeks on end. To some degree, each week we keep seeing the same 1/2000th of our birds over and over again (and missing the same 1999/2000ths of them). There is also the matter that many birds are only in the area for a portion of the year. Some individual long-distance migrants might only spend a few weeks a year in the Lower 48, giving them few chances to be found. So the odds of detecting a single bird over the course of an entire year are not easy to estimate, even in the back-of-the-envelope fashion. Lets just say it is less than 1/40, in most cases probably MUCH less than that. Which means, of course, the great majority of individual birds are never seen or heard by a birder at all in the entire course of their lives.

It is interesting to apply this 10ha/hr rule of thumb to some of the large-scale bird survey projects. For instance, in most State Breeding Bird Atlas (BBA) projects, they had to accept about 10 hrs of coverage in an individual block as "complete." Even with the tireless efforts of the (mosty unpaid!) organizers and all us intrepid field workers, there was just too much land to cover. So in each 20 square km BBA block we saw about 1 square km worth of birds, or only 5% of the total. Given that most States also had to pare down coverage to only 1 out of 6 or even 1 out of 12 blocks, it looks like these State BBA projects probably found less than 1% of the individual breeding pairs of most species. Every single pair found represents 100 or more pairs that were not found; another way to look at it is that a species that had fewer than 100 pairs nesting in a State had a good chance of being missed entirely. A species with only a very few individual breeders (e.g. single digits) would have been quite unlikely to be detected at all.

At the other pole of the year, a typical Christmas Bird Count has on the order of 50-100 party hours of effort. Using the same rule of thumb, this works out to the equivalent 5-10 square km of area covered. A CBC circle has a total area of nearly 500 square km, so again we are looking at only 1-2% of the birds in the circle actually being counted. Even on the megacounts that have something like 400 party hours, this is still only about 10% coverage. It may feel like you are running out of area to cover at the end of the day, but you are in fact only running out of accessible area. All those backyards and roadless or inaccesible lands behind fences are hiding most of the birds. On a transcontiental scale, there are about 1500 CBCs, giving us about 10,000 square km worth of birds. This is about 0.1% of the total land area of the Lower 48. So once again, we find that even in the intensive CBC period, when birders go afield in massive quanities, for every bird counted there are about 1000 birds missed.

Another interesting implication of this is that a single individual bird who does not stay put within a small area is quite unlikely to be found again after it moves on. Exceptions, of course, for birds that are especially conspicuous and/or tied to especially well-covered habitats. But on the whole, even if two birds of the same species are found in two different places within a few days or weeks of each other, they still are probably not the same individual unless you are in extremely heavily birded territory. More likely is either that whatever circumstances led the first bird to stray brought some other birds of the same species with it, or the publicity about the first sighting got observers especially aware and alert so another bird was found that would have been overlooked otherwise (sort of a corollary to the "Patagonia Rest Area Effect").

I realize that these numbers are very crude estimates, and the generalizations are terribly broad. That's what the backs of envelopes are for. Even so, given the large orders of magnitude involved, if you somehow accounted for all these variabilities and powers of 10 one way or the other, the conclusion would stand up:

We see only a tiny fraction of the birds in our Nation. The vast majority of strays and low-density residents are never found by birders. Once lost track of, a single bird is unlikely to be relocated in its lifetime. And species present in extremely small numbers are likely to be entirely overlooked for long periods of time, even if they are ordinary birds with ordinary levels of detectability.

**Footnote: This number is actually just the ratio of a bird's true abundance (birds/ha) to its rate of detection (birds/hr) under a particular set of circumstances. Hence its units are ha/hr. It is just the conversion factor between detection rate and aerial abundance. So a value of 10ha/hr means that a bird with a density of 1 bird/ha will be detected at a rate of 10 birds/hr; similarly a bird that is detected at a rate of 1 bird/hr has a density of 0.1 birds/ha.

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Friday, March 02, 2007

Lifer longings

All these folks stopping by to get their lifer Common Redpoll have me feeling wistful. I don't even want to say how long it has been since I last added a tickie to my ABA list other than by reading about a new split in the literature. I've never been a long-distance chaser. I prefer to see my birds either closer to home or in context on trips to their native lands. For instance, there's a Northern Wheatear 450 miles south of here near Mobile, which I haven't contemplated chasing. Sure, I need it for my ABA list, but I have seen the species in Europe, and this one is apparently hanging out in construction debris in a new subdivision. I'd rather my ABA wheatear be on a rock in the tundra amid arctic scenery, not on a piece of PVC at a construction site, expecially if it's gonna be a 1000 mile trip.

So I've been taking inventory of where and when I still have clusters of potential ABA lifers; regular "uncommon or better" birds in the lands and habitats that are their normal abodes. Running down the Tennessee list was bleak; only 9 species on it at all I haven't seen, and only one or two that merit listing as "casual" rather than "accidental." My single biggest clump is southeastern Arizona. My birding history there has consisted of one morning at Madera Canyon and a few days in Tucson, plus roadsides and industrial parks from an 18-wheeler. There are still 20-25 reasonable possibilities for me on an extended summer trip, depending on whether you count some of the more iffy visitors. The only other big batch is Alaska, but it's really not practical to lump all of Alaska together as one place. I spent a couple of weeks in the interior and southeast one June, which cleaned up most of the general Boreal birds (except for those dang ptarmigans!). So that really leaves me with two discrete Alaska hot spots: the southwestern sea birds and the western "Beringian" tundra. Either of those offers me about 15-17 birds by themselves, or about 23 collectively. Any old world vagrants I stumbled across would probably be cancelled out by "expected" species I missed, of course. Both of those places are long, expensive trips; even starting from Anchorage those are substantial time- and wallet-draining expeditions. So Alaska isn't even penciled in until several years in the future. Maybe Arizona can happen in 2008?

OK now, those two clumps would take care of about 40 or so more tickies. Other than that, it's a few here, and a few there. Texas offers about 7 species, but these are divided between Big Bend, the Edwards Plateau, and the Valley, with only 2 or 3 in each. I have two clusters left in California: a half dozen pelagics, and 4 or 5 in southern California. New England and the Maritimes offer a few also, though only one land bird (Bicknell's Thrush). Florida only really offers two more on the mainland (Snail Kite and Short-tailed Hawk) plus the noddies if I blew more cash for a Dry Tortugas trip. I'm not considering introduced birds; I'll take them if I find them, but I'm not particulaly keen on having my ABA #600 be some australian parrot in a Miami suburb.

My best bet closest to home is a group of six Great Plains birds that I have managed to miss by always living either too far east or too far west: both Prairie Chickens, Yellow Rail, Sprague's Pipit, Baird's Sparrow, and Smith's Longspur. Don't ask how I have managed to be just shy of 600 on my ABA list, and live in Colorado for 10 years, without getting either prairie chicken! Let he who is without jinx birds cast the first stone. I never got Gunnison Sage Grouse either, but in my defense we didn't even know that species existed back then. The pipit and longspur are both available just across the river in Arkansas, and they (along with the rail) have even been known to show up in Tennessee once in a turquoise moon. But it looks like I could actually swing a trip or two to the State just west, Oklahoma, and nab four of those plus maybe even grab a Black-capped Vireo while I'm there. I'd actually love to make a trip to the northern prairies in breeding season to get the pipit, baird's, and rail all in their full nesting glory, but that's a bigger project. So it appears that OK is likely to be in the travel plans during the next year, since this is the closest and cheapest clump to go explore.